Parallel processing and sentence comprehension difficulty

Eye fixation durations during normal reading correlate with processing difficulty but the specific cognitive mechanisms reflected in these measures are not well understood. This study finds support in German readers’ eyefixations for two distinct difficulty metrics: surprisal, which reflects the change in probabilities across syntactic analyses as new words are integrated, and retrieval, which quantifies comprehension difficulty in terms of working memory constraints. We examine the predictions of both metrics using a family of dependency parsers indexed by an upper limit on the number of candidate syntactic analyses they retain at successive words. Surprisal models all fixation measures and regression probability. By contrast, retrieval does not model any measure in serial processing. As more candidate analyses are considered in parallel at each word, retrieval can account for the same measures as surprisal. This pattern suggests an important role for ranked parallelism in theories of sentence comprehension. The authors thank Sabrina Gerth, Roger Levy, Richard Lewis, Joakim Nivre, and Mats Rooth for comments and suggestions on this work. This research was supported by the National Science Foundation Career Award 0741666 to John Hale, and the Deutsche Forschungsgemeinschaft (German Science Foundation) project “Computational models of human sentence processing: A model comparison approach” awarded to Shravan Vasishth and Reinhold Kliegl (2008-2010). This is a preprint of an article whose final and definitive form has been published as Boston, Marisa Ferrara , Hale, John T. , Vasishth, Shravan and Kliegl, Reinhold(2011) 'Parallel processing and sentence comprehension difficulty', Language and Cognitive Processes, 26: 3, 301 — 349, First published on: 17 January 2011 (iFirst) To link to this Article: DOI: 10.1080/01690965.2010.492228 URL: http://dx.doi.org/10.1080/01690965.2010.492228 PARALLEL PROCESSING AND SENTENCE COMPREHENSION DIFFICULTY 2